During the development process leading to spore production in Bacillus subtilis, numerous proteins are synthesized. We have isolated a genetic region which codes for three protein that are synthesized only during differentiation and only in a particular forespore cell compartment. One of these genes codes for glucose dehydrogenase and is part of a bicistronic unit. We have determined the location of the transcription dehydrogenase and is part of a bicistronic unit. We have determined the location of the transcription initiation site as being 12 base pairs from the ribosomal binding site that precedes the first gene of the operon. We have attached beta-galactosidase to the promoter region as reporter gene and incorporated this whole DNA piece into the SP- beta region of the B. subtilis chromosome. Using specific deletion mutations we have then shown that the area from -10 to -35 suffices to control the expression of this operon during sporulation. Further mutations show that only the bases around -10 and -35 are important where those in the middle region could be all replaced by other bases without any effect. The promoter region looks like a typical receptor for a sigma factor and in fact a sigma G factor has been found whose deficiency leads to the absence of glucose dehydrogenase production. Other mutations were used to delete either the glucose dehydrogenase gene or one of the other two genes in order to determine their physiological importance. The gene included in the glucose dehydrogenase operon was thus shown to be essential for spore germination on the combination of glucose, fructose, asparagine, and potassium whereas germination on alanine was not affected. The significance of the other gene is still being studied.